Electrical distribution system with an external multiple input and status unit

ABSTRACT

An electrical distribution system having a load center for programmably and remotely controlling a plurality of circuit breakers, an expander unit coupled to the load center and a plurality of external switches for providing signals to the load center representative of the status of the switches. The load center contains a control module that continually receives inputs from the expander unit via an interface module. It also contains a keyboard and display for programming instructions for closing and opening the individual circuit breakers and for displaying the status of the circuit breakers. The interface module, coupled to the control module, causes the circuit breakers to open and close according to programmed instructions received from the control module or another external device. The expander unit contains a plurality of input circuits coupled to external switches. An expander circuit having a microprocessor receives signals from the input circuits, which are representative of the status of the external switches, and continually provides signals representative of the status of the switches to the load center for the load center to cause the circuit breakers to open and close as a function of the status of the external switches. The expander circuit also continually receives information from the load center about the status of the individual circuit breakers and provides, to a plurality of output terminals, signals representative of the status of the circuit breakers. The output terminals are coupled to a display device for displaying the status of individual circuit breakers. The output terminal also may be used to activate other devices.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 08/378,326 filed on Jan.26, 1995, now abandoned which is a continuation in part of U.S.application Ser. No. 07/723,474, filed on June 28, 1991.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to circuit breakers and moreparticularly to improvements in the control and monitoring of remotelycontrolled circuit breakers.

2. Descriptions of the Related Art

Remotely controlled circuit breakers are commonly used for temporaryinterruption of electrical power to electrical devices during peak usehours and for programmable control. of lighting and other devices incommercial applications. By selectively opening and closing from remotelocations, such circuit breakers can provide energy savings andconvenience of operations over manually operated circuit breakers. Forthese reasons, remotely controlled circuit breakers are increasinglybeing used in various industries and office buildings alike.

Remotely controlled circuit breaker systems typically include a circuitbreaker load-center having circuit breakers wired to a remotely locatedcontrol unit, such as a computer, for monitoring and/or controlling theindividual circuit breakers. U.S. Pat. No. 4,920,476 issued to Brodskyet al. on Apr. 24, 1990, shows a circuit breaker system wherein thewiring is accomplished by using a patch-board within the load-center.Other systems use hard-wiring between each circuit breaker input/outputand a terminal in the remotely located computer. Such systems are notflexible, in that each time the circuit breaker control requirementschange, the wiring and many system components must be reconfigured orreplaced, which can be expensive and burdensome.

The parent co-pending patent application U.S. Ser. No. 07/723,474, filedon Jun. 28, 1991 and assigned to the assignee of this application,provides an electrical power distribution system which solves theabove-noted problems. It includes multiple circuit breakers, each ofwhich is operable by remote control in at least an open and a closedposition. A circuit breaker control circuit having a termination circuitinterprets circuit breaker control signals from an external switchdevice. A circuit breaker driver board controls and monitors the circuitbreaker input means. Data paths are provided for receiving programmingdata from an external device. A switch input data path coupled to thetermination circuit carries circuit breakers switching instructions fromthe termination circuit. The control circuit responds to manual inputinstructions, programming data and circuit breaker switch instructionsaccording to a prioritization scheme. The parent patent application U.S.Ser. No. 07/723,474, filed on Jun. 28, 1991, is incorporated herein byreference.

The above described circuit breaker system is enclosed in a singlepanel, which has a limited capability to accept inputs from variousexternal switches or devices, which in many applications significantlyreduces the capability of such circuit breaker systems. Additionally, nomeans are provided to remotely display the status of individual circuitbreakers or to operate other devices as a function of the status of theindividual circuit breakers.

The present invention provides an electrical distribution system havingthe above described circuit breaker unit or the load panel and anexpander unit. The expander unit enables the circuit breaker unit toutilize a large number of inputs from various external switches and/ordevices. The expander unit also displays the status of the individualcircuit breakers at a remote location and is adapted to drive or operateother devices as a function of the status of the individual circuitbreakers.

SUMMARY OF THE INVENTION

The present invention provides an electrical distribution system havinga circuit breaker unit or a load panel for programmably and remotelycontrolling a plurality of circuit breakers and an expander unit coupledto the load center for continually providing a plurality of inputs tothe load center that are representative of the status of a plurality ofswitches or other devices and for receiving signals representative ofthe status of the individual circuit breakers from the load center anddisplaying such status on a display means at a remote location. Theexpansion unit also is adapted to drive electrical devices as a functionof the status of the circuit breakers.

The load center contains a control module that continually receivesinputs from the expander unit via an interface module. It also containsa display and programming panel for programming instructions for closingand opening the individual circuit breakers. The interface module,coupled to the control module, causes the circuit breakers. to open andclose according to the programmed instructions received from the controlmodule or another remote control means.

The expander unit contains a plurality of input terminal and a pluralityof output terminals. The input terminals are coupled to externalswitches or other devices based upon whose status the circuit breakerswill be opened or closed. An expander circuit having a microprocessorreceives signals from the input terminals, which are representative ofthe status of the external switches, and continually communicates suchinformation to the load center. The expander circuit also continuallyreceives the information from the load center about the status of theindividual circuit breakers and provides signals to the output terminalsrepresentative of the status of the circuit breakers. The outputterminals are coupled to display means for displaying the status ofindividual circuit breakers. The output terminal also may used toactivate other devices.

Examples of the more important features of the invention thus have beensummarized rather broadly in order that detailed description thereofthat follows may be better understood, and in order that thecontributions to the art may be appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present invention, references shouldbe made to the following detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, inwhich like elements have been given like numerals and wherein:

FIG. 1 shows a perspective view of a circuit breaker unit according tothe present invention.

FIG. 2 shows a block diagram of the system shown in FIG. 1, coupled toan expander unit.

FIG. 3 Shows a more specific block diagram of the controller, interfacemodule and the termination board contained in the system shown in FIG.1.

FIG. 4 shows a display panel for use with the controller module.

FIG. 5 shows a block diagram of the expander unit according to thepresent invention.

FIG. 6 shows a circuit block diagram for the expander circuit shown inFIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The electrical distribution system according to the present inventioncontains two parts: a load center or circuit breaker unit and anexpander unit. FIGS. 1-4 relate to the circuit breaker unit and FIGS. 5and 6 relate to the expander unit. In the discussion that follows, thefunctions and operations of the circuit breaker unit are described firstand then the functions and operations of the expander unit aredescribed.

FIG. 1 shows a perspective view of a circuit breaker unit 15 havingmultiple remotely controllable circuit breakers 20 and circuitrycontained in a control module 32 and an interface module 24 to remotelyand programmably control the closing and opening of the individualcircuit breakers 20. The circuit breaker unit 15 is coupled to anexternal expander unit (FIG. 5) by a link 49, preferably via an "RS-232"port. The circuit breaker unit 15 contains a panel board or load centerenclosure 10 which has a plurality of input power lines 12 coupled to apower source (not shown). A plurality of electrical lines or conductors14 exit the enclosure 10, which are coupled to their associated loads,such as lights or other electrical devices. Bus boards 16 and 18, whichmay be implemented on the same board, are disposed in parallel on eachside of the load center for mounting thereon circuit breakers 20. Atleast some of the circuit breakers are adapted to be remotely controlledwhile the remaining circuit breakers may be only manually operable.

A preferred circuit breaker that may be used as a remotely controlledcircuit breaker 20 in the present invention is described in U.S. patentapplication Ser. No. 07/422,050, entitled "Remote Control CircuitBreakers", assigned to assignee of this application, which isincorporated herein by reference. Another circuit breaker that may beused to implement a remotely controlled circuit breaker 20 in thepresent invention is described in U.S. Pat. No. 4,623,859, issued toErickson et al., assigned to assignee of this application, which isincorporated herein by reference.

Each circuit breaker 20 has a plug-in socket that mates or couples toone of a plurality of connectors 22 on the bus boards 16 and 18. Theconnectors 22 are used on the bus boards 16 and 18 to carry motorcontrol and contact status signals, via the interface module 24, to andfrom the circuit breakers 20. Electrical switching devices, such ascontactors or electrical relays, may also be used in place of circuitbreakers 20.

FIG. 2. shows a block diagram of the interface module 24 of the circuitbreaker unit 15 and its interconnection with an expander unit 200,controller 32 and circuit breakers 20. The interface module 24interprets messages from the controller 32 and facilitates the controland monitoring functions from both local and remote locations. Both thecontrol and monitoring functions are accommodated within the interfacemodule 24 using an interface driver board 34. The interface driver board34 provides a communications path between the circuit breakers 20 andthe controller 32, which resides within and as an integral part of theload-center enclosure 10. The controller 32 may communicate with aremotely located control/monitoring device, such as a computer, via atermination board 38. Any control or monitoring signal transmittedbetween the interface driver board 34 and the circuit breakers iscarried by one of two control buses on the bus boards 16 and 18.

The termination board 38 is used to couple the control and monitoringsignals between the interface driver board 34 and any remotely locatedcontrol/monitoring device via the controller 32. Preferably, the controland monitoring signals are transmitted and received using either adirect-wiring (or dry contact) interface, as depicted at port 40. Thiscoupling may also be accomplished using a number of differenttechniques, including, for example, those techniques discussed in U.S.Pat. No. 4,709,339 (issued to Fernandez), and U.S. Pat. No. 07/503,267,issued to Wallis.

FIG. 3 shows an electrical block diagram of the controller 32 and theinterface module 24. The controller 32 includes a microcomputer 53,preferably an 80C31 or 80C32 type available from Intel Corporation,which communicates with a keyboard and display 55 via a bus 53a. Theuser or operator is provided complete control over, and status of, thecircuit breakers 20 through the keyboard and display panel 55.

The controller 32 includes memory means 57, which includes a Read OnlyMemory (ROM") 57a for permanently storing programmed instructionstherein, a Random Access Memory (RAM) 57b in which information maytemporarily be stored and retrieved, and an Electrically ErasableProgrammable Read Only Memory ("EEPROM") 57c for erasably storingcertain programmed instructions. The memory 57 is programmed by the userto contain specific information for operating each of the system'scircuit breakers 20. Preferably, the memory 57 does not store thepresent state of the circuit breakers, since their state may beregularly. accessed from the circuit breakers 20 themselves. However, ahistory of the circuit breaker activity may be recorded in the memory 57for maintenance purposes.

In order to prevent memory endurance problems from limiting the life ofthe system, writes to the memory 57 are limited. Variable data is storedin the RAM as long as possible before any writes to the memory 57 areperformed. Data is only written to the memory 57 at prescribed timesduring the programming mode of the controller 32. During the system runmode, data is not written to the memory 57 so as to prolong the life ofthe memory.

The interface driver board 34 is shown as interfacing with amicrocomputer 72 through an optical isolator 50 to maintain voltageisolation between the circuits and protect the circuits from power-linetransients. A data multiplexer 59 provides electronic programmingcapabilities from a programming computer or station 66 for accessing thecontroller functions. This is preferably accomplished using serialinterface circuitry 61, e.g., for an RS-232 type protocol, between thedata multiplexer 59 and a programmer station 66. The interface driverboard 34 and the controller 32 may be coupled in this manner using aserial protocol to reduce the number of pins required for communicationtherebetween.

The interface driver board 34 further includes a gate array 60 whichcouples the interface driver board 34 through amplifiers 62 to themotors of the remotely controlled circuit breakers 20 in order tosignificantly reduce the number of required driver transistors andprinted circuit board traces. When the interface driver circuitry iscommanded to engage a breaker (i.e., open or close the breakercontacts), the gate array 60 essentially maps the address of the circuitbreaker into a form which will turn on any two of a plurality of poweroutput transistors associated with the gate array 60. Timers within thegate array 60 drive power transistors 62 external to the gate array 60to control the circuit breaker motor engagement time and status readtimes. For example, a pair of power transistors may drive the circuitbreaker motor in either of two directions for a controlled time periodin order to turn the circuit breaker on or off by closing or opening thecontacts of the circuit breakers 20. After the motor drive time periodelapses, the status of the selected circuit breaker is automaticallyread after a specified settle time and is passed to the communicationscircuitry of the gate array 60. Only one circuit breaker is switched ata time, and sets of breakers are turned on or off sequentially.

Because of the limited physical space available for the power drivercircuitry of the gate array 60, a minimum circuit breaker cycle time,i.e., the time. period to complete the tasks and communicationsassociated with a single command, is observed. This cycle time allowsthe power supply 58 to sufficiently recharge the power supply storagecapacitors (which may be located at the input of the -24 Volt regulator)to supply full voltage to the circuit breaker motors.

The status signals provided by the selected circuit breaker 20 arefiltered by noise filters 64 before being provided to the gate array 60,which transmits the circuit breaker status to the controller 32 throughthe optical isolator 50.

In addition to controlling and monitoring the circuit breakers 20 fromthe keyboard and display 55, the circuit breakers 20 may be accessedusing the microcomputer 53 of the controller 32. For such communicationwith the controller 32, the termination board 38 includes amicrocomputer 72 to communicate directly with the microcomputer 53. Asignificant advantage of this arrangement is that it allows a multitudeof remote devices to control and monitor the circuit breakers 20 in thesame manner as with the keyboard and display panel 55.

The termination board 38 includes a communication or input terminal port54. The communication port 54 is coupled to an external network via anoptical isolator 68b and a communication port 68a, such as an RS-485interface. The expander 200 (FIG. 5) is coupled to the interface module24 through the communication port 54 via an RS-232 port, which port alsomay be used to program the circuit breaker unit 15.

The interface module 24 controls all of the circuit breaker activities.In this manner the controller 32 may be used as an optional element,which may be desirable in many applications, especially when programmingis done from remote location. The controller 32 is required when it isdesired to open and close the circuit breakers 20 based on time of theday or for network operations. The microprocessor 72 of the interfacemodule 24 initiates all communications to the gate array 60 by sending atwo byte message, which minimizes communications protocol errors. Thefirst byte of the two transmitted bytes is equivalent for communicationseither to or from the interface driver board 34 or microprocessor 72. Abyte number is placed in the least significant bit position of alltransmitted bytes to reduce the chance of unsynchronized messages.Accordingly, bit zero of the first byte always has a value of zerobecause it indicates the byte number. Bits one through four indicate thecircuit breaker address and are the least significant bits of aparticular circuit breaker address. Bits five through seven are checkbits which are generated to check bits one through four. The format forthe second byte of a message differs depending on whether it is sentfrom the interface driver board 34 or the microprocessor 72. Messagessent from the microprocessor 72 are command bytes. In the second commandbyte, bit zero is always one because it signifies byte two of themessage. Bits one and two are the most significant two bits of thecircuit breaker address. Bits five through seven are generated to checkbits one through four. Bits three and four are encoded with fourpossible commands to the interface driver board 34. The interface modulecommands are to read the motor, read the contact status, open a selectedbreaker or close a selected breaker. When the most significant bit ofthe command code is a zero, the interface driver board 34 only sendsback a status. If the most significant of the two bits is a one, aswitch command is sent to the interface driver board 34.

Messages sent from the interface driver board 34 are status bytes. Thesecond byte of a status message may differ from the second byte of acommand message in bit positions three and four. In a status byte, bitfour is a status and bit three is always zero. These bits indicate thepresence of a motor in the circuit breaker, the status of the contact,i.e., whether a selected breaker has been opened or closed.

If the interface driver board 34 detects an error in either byte one orbyte two, no circuit breaker switching or status reading occurs. An all1's error message is returned and the gate array 60 is reset to wait forthe first byte of the next command. The microprocessor 72 thenretransmits the previous message. Accordingly, if the microprocessor 72sends a read status message, the interface driver board 34 reads thecircuit breaker status and returns the results to the microprocessor. Ifthe microprocessor 72 message is a switch command, the interface driverboard 34 carries out the command by switching the breaker. It then readsand returns the contact status of the selected breaker. The interfacedriver board response to a read status message is the desired status ofthe contacts of the selected circuit breaker. The interface moduleresponse to a switch command is the actual status of the contact afterthe switch has occurred. The microprocessor 72 uses the returnedinformation to ascertain whether the selected circuit breaker hasswitched. If the returned status shows that the contacts are in thewrong state, the microprocessor 72 may be programmed to attempt tocorrect the problem.

A seven bit cyclic hamming code detects errors in the most significantseven bits of a message byte. The byte number bit is excluded becausethere is no available hamming code which will detect seven bits withthree check bits. The exclusion is insignificant since parity detectsany odd bit error in any bit position. If a two bit error occurs in anymessage byte which includes bit zero, the hamming code will detect itbecause the other seven bits of the byte are checked by the code. If acontroller command is retransmitted multiple times and an unexpectedstatus is received from the gate array 60, the controller 32 may beprogrammed to display the error and may then discontinue transmittingthe command thereby assuming that the circuit breaker has failed.

FIG. 4 shows a keyboard and display panel 55 according to the presentinvention, which is preferably implemented as the front panel of ahousing that encloses the controller 32. The system status and programinformation are displayed on a Liquid Crystal (LCD) display 106, whilethe system configuration and programming are performed using a pluralityof selection switches 102 and 104 (each having two positions ("+" and"-")) respectively placed on either side of the display 106. A manualreset button 110 is provided, which may be used to reset the system. Thedisplay 106 is adapted to display the status of each of the circuitbreakers 20, which may be close, open or override. FIG. 4 shows means todisplay status of 42 circuit breakers, which are labeled 1-42. A darkbackground with a light numeral, such as shown by numeral 2, preferablyindicates that the particular circuit breaker is open (off). A lightbackground with a dark numeral, such as shown by numeral 6, indicatesthat the particular circuit breaker is closed (on), and a flashingnumeral indicates that the automatic control of that circuit breaker hasbeen overridden according to programmed instructions. The system mayalso be programmed to override the circuit breakers as a function of asafety mechanism contained within the circuit breaker unit 15, such asthe opening of the circuit breaker contacts if there is excessivecurrent discharge through the circuit breaker. Multiple circuit breakersused as a single circuit breaker in the system are shown by connectedboxes, such a shown by boxes 17 on the display 106.

The circuit breaker unit 15 may be programmed using the display 106 andthe selection switches 102 and 104 as discussed earlier. The system alsomaybe programmed by an external programmer station 66 (FIG. 3). Theprogramming using keyboard and display 55 maybe performed while it isinstalled on the panel board of the system 15 or from a remote locationby linking it to the circuit breaker unit 15 via an appropriatecommunication link (not shown).

Typically, circuit breakers 20 are turned on or off based on an event.Events may be programmed in the system (automatic control), such as timeof day, or signalled by an input change, such as an input from theexpander 200 (FIG. 5), which maybe when a switch coupled to an expanderinput is moved from on to off or vice versa. The controller 32 sendsoutput signals via the interface module 24 to the circuit breakers,turning them on or off, based on the programmed instructions.

During operation, the system may operate under any of three modes: run;manual; and hold. FIG. 4 shows the system in the run mode 112. When thesystem is operating in any of the other modes, location 112 on thedisplay 106 will display such a mode. During the run mode, the circuitbreaker unit 15 responds automatically to events. All system featuresoperate or function as desired in the run mode. In the manual mode, allcircuit breakers 20 are typically turned on and events are logged andthe outputs updated when the mode returns to the run mode. During thehold mode, the control signals are not processed, the circuit breakers20 remain in their existing state, but the events are logged and theoutputs updated when the mode returns to the run mode. Local programmingvia the keyboard and display 55 or remote programming via a network maystill be done in any of the modes.

FIG. 4 shows the status of the circuit breakers and thus displays"status", as shown in location 113 of the display 106. The status screenis the default screen whenever the system is active. When it is desired,the keyboard may be used to change the display to access additionalinformation categorized as: set-up, program, override and diagnostic.

FIG. 5 shows a block diagram of the expander unit 200 according to thepresent invention. The expander unit 200 is placed within a suitableenclosure 220. Input terminal boards 222a and 222b, each respectivelyhaving a plurality of input terminals 224a (1-n) and 224b (i-n) thereon,are placed in the enclosure 220. The input terminals 1-n are coupled toand receive inputs from their associated external switches, such as theswitches for controlling lighting in selected areas or zones in abuilding or from certain other selected devices, via conductors 226. Anoutput terminal module 232, having a plurality of output terminals233(1-m) is placed in the enclosure 220. Each output terminal may beconnected to a status indicator, such as light emitting diodes (LED) vialines 242. Lines 242 may also be used to operate or drive other devices,such as relays or other equipment. Preferably, there is associated aseparate status indicator for each circuit breaker 20 in the circuitbreaker unit 15 for providing status of their associated circuitbreakers 20 at a remote location. Typically, an LED is on when itsassociated circuit breaker is closed and it is off when its associatedcircuit breaker is open.

An expander circuit 230 for controlling the operation of the expanderunit 200 and for communicating with the circuit breaker unit 15 iscoupled to the input terminals 234 via conductors 221a and 221b, to theoutput terminals 233 via conductors 232a, and to the circuit breakerunit 15 via a communication link 49 by an RS-232 port.

A power supply 236, placed within the enclosure 220, and coupled to anexternal A.C. Line (typically 120 V or 227 V) provides dc power,preferably at 5 V and 24 V, to the low voltage components contained inthe expander unit 200 via line 237. A class two barrier 240 shields thelow voltage components from the high voltage lines in the expander unit200. The expander unit 200 also contains a trough or gutter 240a oneither side of the expander unit 200 to accommodate wires and cables toand from the circuit breaker unit 15 in a manner that enables theexpander unit 200 to be installed above or below the circuit breaker.With such an arrangement, power can be supplied from either the right orleft side of the expander unit 200.

FIG. 6 shows the circuit block diagram for the expander circuit 230. Theexpander circuit 230 contains a plurality of input circuits 270, aplurality of output circuits 272, a control/logic circuit 245 and acommunications circuit. The expander circuit 230 converts the input andoutput signals into electronic messages to and from the circuit breakerunit 15. For simplicity, and not as a limitation, functions of theexpander circuit will now be described without reference to filteringand other protection devices contained within such circuit (not shown)as they do not significantly add to the functionality of the system ofthe present invention.

As noted earlier, the expander unit 230 contains multiple input circuits(typically 48) and multiple output circuits (typically 42). However, forsimplicity only one input circuit 270 and one output circuit 272 areshown in FIG. 6, because the remaining input circuits and outputcircuits are identical thereto.

Each input circuit 270 contains two separate circuits that may belogically associated with each other for the purpose of interpreting athree-wire switch 276, which is preferably used as an input terminal inthe expander unit 200. Thus, in an expansion unit with 48 inputs, therewill be a total of 96 input circuits. A typical input circuit contains avoltage divider 240 and an input buffer 244. An input is referred to as"on" when an externally connected device, such as a switch 275, to theinput circuit 270 is closed, and "off" when it is open. In FIG. 6, theswitch 275 is shown to be in the open position. The switch 275 isconnected to a common low voltage line, typically 24 Vdc, which voltagealso in connected to the common terminals of all of the three wireswitches 276 contained in the expander unit 200.

The voltage divider 240 reduces the 24 Vdc to approximately 5 Vdc, whichis the voltage used to operate commercially available buffer chips, suchas the buffer 244. The output side of the buffer 244 provides a binaryoutput state of "1" or "0," representing the state of the input. Thestate 1 maybe, defined as on, i.e., corresponding to. an on switch 275and the state 0 may be defined as off, i.e., corresponding to an offswitch 275 or vice versa. The buffer output is applied to amicrocontroller circuit 246 via an address and data bus 250.

Each of the output circuits 272 in the expander circuit 230 essentiallyis an electronic switch 266 that may be turned on or turned off. A load,such as a lamp 252 or a relay or some other device, may be coupledbetween the 24 Vdc common low voltage and the output switch 266. Anoutput switch and latch circuit 264 holds the derived state of theoutput switch 266, which is periodically updated by the microcontrollercircuit 246. The output switch and latch circuit 264 contains circuitrywhich limits the current to output drivers contained therein that drivedevices 252 and circuitry that limits the maximum current that may besupplied by the power supply.

The control and logic circuit 245 of the expander circuit 230 includesthe microcontroller circuit 246, which contains a suitablemicroprocessor. The microcontroller circuit 246 is coupled via theaddress and data bus 250 to a program memory 254 (preferably ROM), adata memory 256 (preferably RAM) and an address logic circuit 258. Thecontrol and logic circuit 245 continually communicates the status ofeach of the input circuits 270 to the circuit breaker unit 15 via acommunication circuit 260. It also continually provides signals to theoutput devices 252 representative of the status of their associatedcircuit breakers 20. The microcontroller circuit 246 executes programmedinstructions (program) resident in the program memory 254. The residentprogram in the microcontroller circuit 246 is used to implement theoperation of the expander unit 200.

The communications circuit 260 preferably includes a level translatorthat is used to drive a communication bus 262 coupled to the circuitbreaker unit 15 via the port 40 on the interface module 24 (FIG. 2). Thecommunication circuit 260 preferably works with a Universal AsynchronousReceiver Transmitter ("UART") to send and receive serial messages. TheUART is preferably combined with the microprocessor and located withinthe microprocessor chips.

During operation, the microcontroller circuit 246 continually receivesinputs from each of the multiple input circuits 270 and determines ifthere has been any change in the input status, i.e., a change from anopen position to a closed position of the switch 245 or vice versa. Themicrocontroller circuit then implements communication to and from thecircuit breaker unit 15 via the communications circuit 260. The expandercircuit 230 always initializes communications with the circuit breakerunit 15. The preferred communication messages from the expander circuit230 to the circuit breaker unit 15 are: Write Input, which is a prioritymessage is sent as the next message after an input event occurs; ReadOutput State, which is a periodic message is sent at predeterminedintervals, typically once per second; Read Input Type, which is abackground message is sent sequentially when no other messages arepending; and Write Diagnostic Status, which also is a background messageis sent sequentially when no other messages are pending.

Communication activity from the expander unit 200 to the circuit breakerunit 15 is continuous. Background messages are sent sequentially toobtain the input type configuration from and provide to the expanderunit diagnostic status of the circuit breaker unit 15. An expander unit200 having 48 input terminals will result in a "list" of 49 messagesthat continually repeat, one message for diagnostic status and onemessage for each of the 48 inputs of the expander unit 200. This allowsthe expander unit 200 to react to an input type change or reportdiagnostic errors on a periodic basis. Although the list repeats,another message may be inserted into the list. The Read output statemessage is inserted periodically so that the expander unit 200 has anup-to-date copy of the status of each of the circuit breakers 20. Thisstatus is likewise periodically written to the latch in the outputswitch and circuit 264. The Write Input message has the highest priorityand is inserted as the next message. This is to provide quick responseof the circuit breaker unit 15, when a switch 245 is opened or closed.

A priority Write Input message is generated as a result of a series ofevents. First, if there is a physical change of state at one of theinput circuits 270. This change is detected as the microcontrollercircuit 246 performs its periodic polling of all input circuits 270. Anynew state of the input is interpreted into either an "on" or "off"signal. This requires the Input Type setup information that was readfrom the circuit breaker unit 15 (for example, momentary push-buttonswitches toggle the state on each momentary closure, but maintainedswitches are on when closed, and off when open). After interpretationoccurs, the Write Input message is built that contains the input numberand the new state, and the communications task is signaled that apriority message is ready.

The expander unit's communications port is connected to the expanderport on the circuit breaker unit 15. The microprocessor 72 in theInterface Module 24 (FIG. 3) provides communications at this port. Itreads and writes the status as requested. In the event of a Write Inputmessage, bits are set inside the Interface Module 24 to record the inputstate sent from the expander unit 200, as well as the fact that atransition has occurred. This will trigger the breaker control task thatwill match the input to the list of individual circuit breakers 20 thatare affected by that input. Circuit breakers 20 will turn on or off asprogrammed in the circuit breaker unit 15, which program includesturning on and off the circuit breakers as a function of the status ofthe input switches 270, which in turn depends upon the status of devicesconnected thereto.

In summary, the circuit breaker unit 15 controls the operation of thevarious circuit breakers 20 in accordance with the programmedinstructions contained in the circuit breaker unit or received from aremote device. An expander unit that is external to the circuit breakerunit continually communicates to the circuit breaker unit 15 the statusof a plurality of switches 270 or other devices and in response theretothe circuit breaker unit 15 controls the operation of the circuitbreakers in accordance with the programmed instructions. The expanderunit 20 continually receives signals from the circuit breaker unit 15that are representative of the status of the individual circuit breakersand displays such status at a remote location and/or activates oroperates other devices as a function of the status of the circuitbreakers.

The foregoing description is directed to particular embodiments of thepresent invention for the purpose of illustration and explanation. Itwill be apparent, however, to one skilled in the art that manymodifications and changes to the embodiment set forth above are possiblewithout departing from the scope and the spirit of the invention. It isintended that the following claims be interpreted to embrace all suchmodifications and changes.

What is claimed is:
 1. A circuit arrangement for use with an electrical distribution unit used to control current paths through a plurality of associated electrical switching devices, each such switching device operable in an open position and a closed position:(a) a plurality of input circuits, each said input circuit adapted to be coupled to an associated external element having an on state and off state, each said input circuit generating signals representative of the on state and the off state of its associated external element; (b) a control and logic circuit coupled to the electrical distribution unit and the input circuits for receiving therefrom digital signals representative of the on and off states of the external elements associated with said input circuits, said control and logic circuit continually providing digital signals representative of the on and off states of the external elements to the electrical distribution unit to operate the switching devices between their respective open and closed positions corresponding to the on and off states of the external elements, said control and logic circuit receiving from the electrical distribution unit digital signals for each of the switching devices which are representative of the open and closed positions of each such switching devices; and (c) a separate output terminal corresponding to each of the switching devices in said plurality of switching devices coupled to the control and logic circuit for receiving therefrom digital signals representative of the open and close position of their corresponding switching devices.
 2. A circuit arrangement for use with an electrical distribution unit used to control current paths through a plurality of associated electrical switching devices, each such switching device operable in an open position and a closed positions, comprising:(a) a plurality of input terminals, each said input terminal adapted to be coupled to an associated external element having an on state and an off state; (b) a control and logic circuit coupled to the electrical distribution unit and the input terminals receiving therefrom digital signals representative of the on and off states of the external elements to the electrical distribution unit for the electrical distribution unit to operate the switching devices between their respective open and closed positions as a function of the on and off states of the external elements, said control and logic circuit receiving from the electrical distribution unit separate digital signals for each of the switching devices which are representative of the open and closed positions of each such switching devices; and (c) a separate display device corresponding to each of the switching devices in said plurality of switching devices coupled to the control and logic circuit for receiving therefrom signals representative of the open and close positions of their corresponding switching device and in response thereto indicating the open and close status of their associated switching device.
 3. An electrical distribution system, comprising:(a) a circuit breaker enclosed in a load panel having a plurality of circuit breakers, each said circuit breaker operable in an open and closed position, said circuit breaker unit further having an interface module coupled to each of the circuit breakers, said interface module causing the circuit breakers to operate between their respective open and closed positions in response to programmed instructions; and (b) an expander unit external to the load center panel and electrically coupled to the interface module, said expander unit providing signals to the interface module representative of an on state and an off state of a plurality of external devices for the interface module to cause the circuit breakers to operate between their respective open and closed positions as a function of the on and off states, said expander unit receiving signals from the interface module representative of the open and close position of the circuit breakers and in response thereto causing a display device to separately indicate the open and closed position of each of the circuit breakers.
 4. A circuit breaker unit, having a panel board with a plurality of power lines connected to an external power source, connected to an expander unit that provides digital signals to the circuit breaker unit on the status of external devices, comprising:(a) a plurality of remotely controllable circuit breakers; (b) a control module; (c) an interface module;each of the remotely controllable circuit breakers being capable of interrupting the flow of electricity through an associated power line; the interface module being connected to the control module, the expander unit and the circuit breakers; the interface module being capable of causing the circuit breakers to open and close according to instructions received from the control module and having the capability of sending a digital signal to the control module indicating the status of each of the circuit breakers and of status signals received from the expander unit; and the control module being capable of sending instructions to the interface module to open and close the circuit breakers according to programmed instructions stored in the control module, the status of each of the circuit breakers and the status signals received from the expander unit.
 5. The circuit breaker unit of claim 4 wherein the programmed instructions are stored in the control module on a memory selected from (i) an Electrically Erasable Programmable Read Only Memory (EPROM), (ii) a random access memory (RAM), and, (iii) a read only memory (ROM).
 6. The circuit arrangement of claim 1 wherein the switching devices are circuit breakers, further comprising a bus board for mounting the circuit breakers thereon.
 7. The circuit arrangement of claim 1 wherein the electrical distribution unit receives signals from control and logic circuit by means of a data port.
 8. The circuit arrangement of claim 1 further comprising a data multiplexer for multiplexing of signals between the control and logic circuit and the electrical distribution unit.
 9. The circuit arrangement of claim 2 wherein the switching devices are circuit breakers, further comprising a bus board for mounting the circuit breakers thereon.
 10. The circuit arrangement of claim 2 wherein the electrical distribution unit receives signals from control and logic circuit by means of a data port.
 11. The circuit arrangement of claim 2 further comprising a data multiplexer for multiplexing of signals between the electrical distribution unit and the control and logic circuit.
 12. The electrical distribution system of claim 3 further comprising a bus board for mounting the circuit breakers thereon.
 13. The electrical distribution system of claim 3 wherein the expander unit sends signals to the load center panel by means of a data port.
 14. The electrical distribution system of claim 3 further comprising a data multiplexer for multiplexing of signals between the expander unit and the load center panel.
 15. The circuit breaker unit of claim 4 further comprising a bus board located within the panel board for mounting the circuit breakers thereon.
 16. The circuit breaker unit of claim 4 further comprising a data port for providing communication between the expander unit and the circuit breaker unit.
 17. The circuit breaker unit of claim 4 further comprising a data multiplexer for multiplexing of signals between the expander unit and the circuit breaker unit.
 18. The circuit breaker unit of claim 4 further comprising a communications circuit in the expander unit, said communications circuit adapted to work with a Universal Asynchronous Receiver Transmitter to send and receive serial messages.
 19. The circuit breaker unit of claim 4 wherein communication activity from the expander unit to the circuit breaker unit is continuous.
 20. A method of controlling power to a plurality of power lines connected to an external power source comprising:(a) connecting a circuit breaker unit, having:(i) a panel board with a plurality of remotely controllable circuit breakers each of the remotely controllable circuit breakers being capable of interrupting the flow of electricity through an associated the power line, (ii) a control module; and (iii) an interface module; to the plurality of power lines; (b) connecting an expander unit to the circuit breaker unit, (c) providing from the expander unit to the circuit breaker unit digital signals on the status of external devices; (d) connecting the interface module to the control module, the expander unit and the circuit breakers, the interface module being capable of causing the circuit breakers to open and close according to instructions received from the control module; (e) sending from the interface module to the control module a digital signal indicating the status of each of the circuit breakers and of status signals received from the expander unit; and (f) sending instructions from the control module to the interface module to open and close the circuit breakers according to programmed instructions stored in the control module, the status of each of the circuit breakers and the status signals received from the expander unit. 